From 569372494abebe531fa8bc76e09454dbde47ae48 Mon Sep 17 00:00:00 2001
From: Anthony Templeton <twantempleton11@gmail.com>
Date: Mon, 30 Mar 2026 09:02:32 -0400
Subject: [PATCH] feat: uslp ccsds standard

---
 src/Ccsds.zig | 37 ++++++++++++++++++++--------
 src/Uslp.zig  | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 95 insertions(+), 10 deletions(-)
 create mode 100644 src/Uslp.zig

diff --git a/src/Ccsds.zig b/src/Ccsds.zig
index a68a3ff..525cf97 100644
--- a/src/Ccsds.zig
+++ b/src/Ccsds.zig
@@ -4,6 +4,7 @@ const std = @import("std");
 
 const Ccsds = @This();
 
+packetType: pktType,
 header: HeaderMetadata,
 primaryHeader: []const u8,
 secondaryHeader: ?[]const u8,
@@ -13,6 +14,24 @@ allocator: std.mem.Allocator,
 
 pub fn init(pl: []const u8, allocator: std.mem.Allocator, config: ?Config) !Ccsds {
     var rawPackets = try allocator.dupe(u8, pl); // dupe so it doesn't go out of scope too early
+    const primaryHeader = rawPackets[0..6];
+    const headers = fetchHeader(rawPackets, config);
+    const end = 5 + headers.header.packetSize; // num of header bytes + packet_size
+    const packets = rawPackets[headers.start..end];
+
+    _ = allocator.resize(rawPackets, end);
+
+    return .{
+        .header = headers.header,
+        .primaryHeader = primaryHeader,
+        .secondaryHeader = headers.secondaryHeader,
+        .packets = packets,
+        .rawData = rawPackets,
+        .allocator = allocator,
+    };
+}
+
+pub fn fetchHeader(rawPackets: []u8, config: ?Config) struct {header: HeaderMetadata, secondaryHeader: ?[]const u8, start: u8} {
     const primaryHeader = rawPackets[0..6];
     const version = @as(u3, @truncate((primaryHeader[0] >> 5) & 0x07));
     const packetType = @as(u1, @truncate((primaryHeader[0] >> 4) & 0x01));
@@ -46,18 +65,11 @@ pub fn init(pl: []const u8, allocator: std.mem.Allocator, config: ?Config) !Ccsd
         .packetSequenceCount = packetSequenceCount,
         .packetSize = packetSize + 1,
     };
-    const end = 5 + header.packetSize; // num of header bytes + packet_size
-    const packets = rawPackets[start..end];
-
-    _ = allocator.resize(rawPackets, end);
 
     return .{
-        .header = header,
-        .primaryHeader = primaryHeader,
-        .secondaryHeader = secondaryHeader,
-        .packets = packets,
-        .rawData = rawPackets,
-        .allocator = allocator,
+        .header = header, 
+        .secondaryHeader = secondaryHeader, 
+        .start = start,
     };
 }
 
@@ -83,6 +95,11 @@ pub const HeaderMetadata = packed struct {
     packetSize: u16,
 };
 
+pub const pktType = enum {
+    spacePkt,
+    uslp
+};
+
 /// If you choose to use the CCSDS config you need to call this function first to get the Config struct
 pub fn parseConfig(configContent: []const u8, allocator: std.mem.Allocator) !Config {
     const configParsed = try std.json.parseFromSlice(Config, allocator, configContent, .{});
diff --git a/src/Uslp.zig b/src/Uslp.zig
new file mode 100644
index 0000000..877c88c
--- /dev/null
+++ b/src/Uslp.zig
@@ -0,0 +1,68 @@
+const std = @import("std");
+
+pub const Uslp = @This();
+
+primaryHeader: USLPHeader,
+insertZone: []const u8,
+dataHeader: DataHeader,
+TFDZ: []const u8,
+OpControl: u32,
+FrameError: u16,
+rawData: []const u8,
+allocator: std.mem.Allocator,
+
+pub fn init(pl: []const u8, allocator: std.mem.Allocator) !Uslp{
+    var rawPackets = try allocator.dupe(u8, pl); // dupe so it doesn't go out of scope too early
+    const primaryHeader = rawPackets[1..6];
+    const headers = fetchHeader(rawPackets);
+    const end = 5 + headers.header.packetSize; // num of header bytes + packet_size
+    const packets = rawPackets[headers.start..end];
+
+    _ = allocator.resize(rawPackets, end);
+
+    return .{
+        .header = headers.header,
+        .allocator = allocator,
+        .rawData = rawPackets,
+    };
+}
+
+pub fn deinit(self: *Uslp) !void {
+    self.allocator.free(self.rawData);
+}
+
+pub fn fetchHeader(rawPackets: u8) struct {header: USLPHeader } {
+    const header = rawPackets[0..6];
+    const tfv = @as(u4, @truncate((header[0] >> 5) & 0x07));
+    std.debug.print("%s", .{tfv});
+    // const tfvn = rawPackets[0..3];
+    // const scid = rawPackets[3..19];
+}
+
+pub const DataHeader = packed struct {};
+
+pub const USLPHeader = packed struct {
+    xferFrameVersion: u4,
+    scID: u16,
+    srcID: u1,
+    virtChannel: u6,
+    mapID: u4,
+    eofFlag: u1,
+    frameLength: u16,
+    bypassCntrl: u1,
+    protocolCmd: u1,
+    spare: u2,
+    ocf: u1,
+    VCFrameCountLength: u3,
+    VCFrameCount: u56,
+};
+
+
+test "CCSDS Structure Testing w/o config" {
+    const raw_test_packet: [16]u8 = .{ 0x78, 0x97, 0xC0, 0x00, 0x00, 0x0A, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A };
+    var converted_test_packet = try Uslp.init(&raw_test_packet, std.testing.allocator, null);
+    defer converted_test_packet.deinit();
+
+    try std.testing.expectEqual(3, converted_test_packet.header.version);
+
+}